Belt drive for auxiliary units of an internal combustion engine

ABSTRACT

A belt drive for a secondary unit of an internal combustion engine includes a friction wheel drive having a friction wheel, a cam device for adjusting the engagement of the friction wheel to the drive wheel of the secondary unit, the cam device having a cam, a swivel arm by which the friction wheel is connected to the cam which is rotationally mounted on a side of the engine, and a spring biasing the swivel arm in a tension direction. The friction wheel is in permanent position of frictional engagement with a drive wheel of the secondary unit to drive the secondary unit and with an outside of a belt on a drive wheel of the internal combustion engine or of another secondary unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/EP2003/011405, filed Oct. 15, 2003, designating the UnitedStates of America, and published in German as WO 2004/048759 A1, theentire disclosure of which is incorporated herein by reference. Priorityis claimed based on German Patent Application No. 102 55 074.3, filedNov. 26, 2002.

SUMMARY AND BACKGROUND OF THE INVENTION

The invention relates to a belt drive for auxiliary units of an internalcombustion engine with which a friction wheel drive is associated fordriving a secondary unit provided separately on the internal combustionengine and whose drive wheel cooperates frictionally with a frictionwheel, the friction wheel being arranged for adjustment relative to thedrive wheel with regard to frictional contact.

DE 39 34 884 A1 discloses a blet drive, wherein the friction wheel isdriven through a belt tightener in the belt drive. The friction wheelthus driven indirectly by the belt is arranged with the belt tighteneron a rocking lever, while for uncoupling the clamping roll adjustmentfrom the friction wheel adjustment to the secondary unit's drive wheel,an eccentric device serves, which is adjustable by hand in case of need,independently of the clamping roll adjustment.

Also, unpublished patent application P 102 36 746 discloses a belt drivewith a friction wheel arrangement in which a friction wheel frictionallycooperating with the outside of the belt in the wrap-around portion ofthe belt is also in frictional driving communication with the drivewheel of a separate secondary unit. Information for sustaining adriving, permanent position of engagement of the friction wheel with thedrive wheel on the one hand and with the belt on the other cannot belearned from this document.

An object of the invention is to offer a constructionally simplereadjusting device for a friction wheel cooperating directly by frictionwith a belt for driving a separate secondary unit to achieve of a properpermanent engagement position of the friction wheel.

The object is achieved in that the friction wheel also cooperates withthe outer side of the belt in the area of its contact with a drivingwheel of the internal combustion engine or auxiliary unit, and is heldin a permanent position of engagement with driving wheel and belt by arocking lever journaled at the machine end on a cam arranged for rotarymovement, while the cam of the readjusting device, driven in rotationunder the effect of a spring bias, acts upon the rocking lever in thetensional or pressing direction with spring bias in the correspondingdirection.

With the invention a structurally simple readjustment device isadvantageously achieved, whose further advantage is a compactconfiguration.

An advantageously great readjustment range is achieved if the cam ismounted with an eccentricity directed transversely of the tension orpressure direction of the rocking lever as its starting position.

Also, a compact cam system is advantageously achieved in that therocking lever is journaled by an eye formed in the end section remotefrom the friction wheel, which is equipped in a recess coaxial with thecam axis with a biased coil turning spring, while the coil spring fixedat one end on the machine side is disposed for rotating action at theother end on the cam.

Furthermore, for the achievement of a readjustment device that is lightand small, it is proposed that the cam formed from a plastic be mountedfor rotation on a metal sleeve disposed in a recess and receiving thecoil spring, which is disposed nonrotationally through an end section ofthe rotational helical spring passing through the bottom of the metalsleeve and entering conformingly into a cavity on the machine side, andfurthermore is fastened, by a threaded bolt coaxial with the cam axiswith the interposition of a fastening cover of the cam device, drivinglyagainst an abutment surface on the machine side, and the cam is disposedon the metal sleeve between abutment surface and the fastening coverwith axial clearance.

For an advantageously simple construction of the cam device provision ismade according to the invention that the metal sleeve has on thefastening cover a marginal cut-out fitted circumferentiallycorresponding to the adjustability of the friction wheel for the freepassage of an end section of the helical spring directed transversely tothe cam axis for rotational engagement with the cam, and that the metalsleeve has an additional marginal cut-out for the engagement of anantirotational projection disposed on the fastening cover.

For an adjusting device of short and light-weight construction, theinvention furthermore provides that the cam is in connection with theeye of the rocking arm formed from a plastic, with the interposition ofa friction bearing sleeve, which is formed relatively close to the eye,with a fork-like friction wheel pickup, and that the cam device of theshort-construction rocking arm is disposed between the secondary unit'sdrive wheel and the drive wheel partly covered by the drive belt on aknob provided on the front of the internal combustion engine. Aspace-saving arrangement of the adjusting device is thus also achieved.

Lastly, a proposal of the invention is based on the fact that thefriction wheel comprises a spoked wheel body formed from plastic, with asupport of a rubber material disposed on the external circumference, thespoked wheel body being supported through an integrated, encapsulatedrolling bearing against a bearing pin of the fork of the rocking arm.

The invention is described with the aid of a preferred embodimentrepresented in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents an internal combustion engine with a friction wheelwith an adjusting device according to the invention.

FIG. 2 shows a section taken along line II-II through the cam system ofthe adjusting device.

FIG. 3 shows an exploded representation of the adjusting device with thecam system, and

FIG. 4 shows the cam system open at the end to show the cam rotatableunder spring stress for readjustment of the friction wheel.

DETAILED DESCRIPTION OF THE DRAWINGS

A belt drive 1, shown only in sections, for auxiliary units of aninternal combustion engine 2 shown only section-wise, comprises afriction wheel drive 3 for driving a secondary unit 4 providedseparately on the internal combustion engine, which is preferably acoolant pump. The secondary unit 4 has a drive wheel 5 which cooperateswith a friction wheel 6 of the friction wheel drive 3 driven on the beltside.

As seen in FIG. 1, the friction wheel 6 furthermore cooperatesfrictionally with the outside of the belt 1′ in the wrap-around portionof a drive wheel 7 of the internal combustion engine 2 or an auxiliaryunit. Also, the friction wheel 6 is held in a position of permanentengagement with drive wheel 5 and belt 1′, by a cam 8 disposed forrotation on the machine side, while the cam 8 of the adjusting device11, driven in rotation under the action of a biased spring 10, acts onthe rocking arm 9 in the pulling direction of in the pushing directionaccording to the spring bias directed accordingly. Preferably, in theadjusting device 11 shown in FIGS. 1-4 the friction wheel 6 is held in apermanently engaged position by means of the cam 8, spring-loadedcounterclockwise, through the rocking arm 9 which is biased tensionally.

To achieve a relatively great adjustment range, the cam 8 is mountedwith an eccentricity “e” directed across the pulling direction of thearm 9 as its initial position.

For a compact adjusting device 11, the rocking arm 9 is mounted at aneye 12 formed in the end section remote from the friction wheel 6 on thecam 8 which is equipped with a biased coil spring 10′ in a recess 14coaxial with the cam axis 13, the coil spring 10′ held fixed on themachine at one end, the coil spring 10′ fixed at one end on the machineis disposed at the other end on the cam 8, acting for rotation.

A cam device 8′ of small and light construction is furthermore achievedby the fact that the cam 8, formed from a plastic, is mounted forrotation on a metal bush 15 accommodating the coil spring 10′ anddisposed in its recess 14. The metal bush 15 is rotationally fixedthrough an end section 17 of the coil spring 10′ engaging conforminglyin a cavity 16 on the machine side and furthermore, through a bolt 18coaxial with the cam axis 13, with the interposition of a washer 19, itis driven against an abutment surface 20. Furthermore, the cam 8 isdisposed on the metal bush 15 between the abutment surface 20 and thewasher 19.

Furthermore, the aforesaid metal bush 15 has on the securing cover sidea marginal section 21 appropriately adapted in the circumferentialdirection for the adjustability of the friction wheel 6 for the freepass-through of an end section 22 directed transversely of the cam axis13 of the coil spring 10′ for rotatory engagement of the cam 8. Themetal bush 15 has an additional marginal notch 23 for engaging anantirotational projection 24 which prevents any co-rotation of thewasher 19 when the bolt 18 of the eccentric device 8′ is tightened.

As FIGS. 2 and 3 show, the cam 8 is joined with the interposition of abushing 26 to the eye 12 of the arm 9 formed of plastic, which isrelatively closely adjacent the eye 12 with a fork-like friction wheelsocket 26. The compact eccentric device 8′ makes it possible to arrangethe adjusting device 11 with the short arm 9 between the secondaryunit's drive wheel 5 and the drive wheel 7 partially wrapped around bythe belt 1′ on a post 27 provided on the end of the internal combustionengine 2, for the achievement of an advantageous utilization of space.

Lastly, especially FIGS. 1 and 4 show that the friction wheel comprisesspoked wheel bodies 28 formed of plastic, with a cover 29 of a rubbermaterial disposed on its outer circumference. Also, the spoked wheel 28is supported against a bolt 30 of the swiveling arm's fork 26 through anintegrated and encapsulated roller bearing 31.

With the invention, a lightweight adjusting device 11 of advantageouslysimple design requiring little space is achieved.

The foregoing description and examples have been set forth merely toillustrate the invention and are not intended to be limiting. Sincemodifications of the described embodiments incorporating the spirit andsubstance of the invention may occur to persons skilled in the art, theinvention should be construed broadly to include all variations fallingwithin the scope of the appended claims and equivalents thereof.

1. A belt drive for a secondary unit of an internal combustion engine, comprising: a friction wheel drive having a friction wheel, wherein the friction wheel is in permanent position of frictional engagement with a drive wheel of the secondary unit to drive the secondary unit and with an outside of a belt on a drive wheel of the internal combustion engine or of another secondary unit; a cam device for adjusting the engagement of the friction wheel to the drive wheel of the secondary unit, the cam device having a cam; a swivel arm by which the friction wheel is connected to the cam which is rotationally mounted on a side of the engine; a spring biasing the swivel arm in a tension direction.
 2. The belt drive according to claim 1, wherein the cam is mounted with an eccentricity that is on the opposite side of the tension direction of the swivel arm relative to the center of rotation of the cam as starting position.
 3. The belt drive according to claim 2, wherein the swivel arm is journaled through an eye formed in an end section remote from the friction wheel on the cam which has a recess coaxial with the cam axis with the spring that is under bias, and wherein the spring is fixed at one end on the engine side and is disposed at the other end acting rotationally on the cam.
 4. The belt drive according to claim 3, wherein the cam is made of a plastic and is journaled for rotation on a metal bush that is disposed in the recess and accommodates the spring, wherein an end of the spring passes through the bottom of the metal bush and is fixed against rotation engaging conformingly in a cavity on the engine side, wherein through a bolt coaxial with the eccentric axis with the interposition of a cover of the eccentric device is forcibly abutted against an abutment surface on the engine side, and wherein the cam between the abutment surface and the protective cover is disposed with axial free play on the metal bush.
 5. The belt drive according to claim 4, wherein the metal bush has on the cover side a marginal cutout corresponding to the adjustability of the friction wheel adapted accordingly in the circumferential direction for the free passage of the other end, pointing transversely of the cam axis, of the oil spring for rotational attachment to the cam, and wherein the metal bush has a wider marginal cutout for engagement by an antirotational projection disposed on the protective cover.
 6. The belt drive according to claim 5, wherein the cam is in connection with the eye of the arm, with the interposition of an antifriction bushing, which arm is formed relatively closely to the eye with a fork-like friction wheel receiver, and wherein the cam of the arm is disposed between the secondary unit's drive wheel and the drive wheel partially wrapped around by the belt is arranged on a post provided at the face of the internal combustion engine.
 7. The belt drive according to claim 6, wherein the friction wheel comprises a spoked wheel formed of plastic, having a covering of a rubber material arranged on the outside circumference, and wherein the spoked wheel is urged against a bolt of the fork of the arm through an integrated and encapsulated rolling bearing.
 8. The belt drive according to claim 1, wherein the swivel arm is journaled through an eye formed in an end section remote from the friction wheel on the cam which has a recess coaxial with the cam axis with the spring that is under bias, and wherein the spring is fixed at one end on the engine side and is disposed at the other end acting rotationally on the cam.
 9. The belt drive according to claim 8, wherein the cam is made of a plastic and is journaled for rotation on a metal bush that is disposed in the recess and accommodates the spring, wherein an end of the spring passes through the bottom of the metal bush and is fixed against rotation engaging conformingly in a cavity on the engine side, wherein through a bolt coaxial with the eccentric axis with the interposition of a cover of the eccentric device is forcibly abutted against an abutment surface on the engine side, and wherein the cam between the abutment surface and the protective cover is disposed with axial free play on the metal bush.
 10. The belt drive according to claim 9, wherein the metal bush has on the cover side a marginal cutout corresponding to the adjustability of the friction wheel adapted accordingly in the circumferential direction for the free passage of the other end, pointing transversely of the cam axis, of the oil spring for rotational attachment to the cam, and wherein the metal bush has a wider marginal cutout for engagement by an antirotational projection disposed on the protective cover.
 11. The belt drive according to claim 9, wherein the cam is in connection with the eye of the arm, with the interposition of an antifriction bushing, which arm is formed relatively closely to the eye with a fork-like friction wheel receiver, and wherein the cam of the arm is disposed between the secondary unit's drive wheel and the drive wheel partially wrapped around by the belt is arranged on a post provided at the face of the internal combustion engine.
 12. The belt drive according to claim 1, wherein the friction wheel comprises a spoked wheel formed of plastic, having a covering of a rubber material arranged on the outside circumference, and wherein the spoked wheel is urged against a bolt of the fork of the arm through an integrated and encapsulated rolling bearing. 